A protocol for rapid evidence synthesis into soil loosening as an … · 2018-09-07 · A protocol...

A protocol for rapid evidence synthesis into soil loosening as an intervention to ameliorate

compaction caused by dairy farming and the impacts of this for productivity and

sustainability

Kendall, H1., Taylor, A. E2., Reed, M1. Stewart, G1

1 School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU.

2 Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK

Corresponding authors: Helen Kendall; [email protected]

Abstract

This is a protocol for a rapid review of the effectiveness of soil loosening to ameliorate

compaction caused by cattle treading from dairy production on UK dairy farms. The review

will synthesize relevant literature that explores the impacts that can be derived from

mechanical soil loosening for improved soil quality, productivity (i.e. yield) and the

environment. The protocol outlines the rationale, objectives, inclusion criteria, search

strategy and screening processes for the meta-analysis, and the plans for data extraction, risk

of bias and data synthesis approaches.

PeerJ Preprints | https://doi.org/10.7287/peerj.preprints.27180v1 | CC BY 4.0 Open Access | rec: 7 Sep 2018, publ: 7 Sep 2018

1. Protocol

1.1 Introduction Soil compaction is significant cause of soil degradation globally (Drewry and Paton, 2000, FAO,

2015, Smith et al., 2013, Wentworth, 2015) Compaction results in the underlying soil structure

being unable to withstand the pressures applied to it. Compression leads to coarsening of the

soil, loss of the structural units of the soil, decrease in soil volume (erosion), an increase in

bulk density, decrease in porosity and a reduction in the hydraulic capacity of the soil (NFU,

2016, DEFRA, 2008, Newell-Price et al., 2013). Soil structures and quality vary according to

soil type (i.e. clay, sand, silt, loams and peat) and location with varying levels of susceptibility

to compaction damage (Bezuidenhout, 2010, Drewry, 2006, DEFRA, 2008, Wentworth, 2015,

Drewry et al., 2004, Newell-Price et al., 2013). The macroporosity of soil (the volume of pores)

is used by experts as an indicator of soil compaction. In arable land compaction and the

reduction of soil macroporsity (below 10%) represent poor aeration and results in cultivation

difficulties as a result of restricted water and nutrient delivery, and reduced earthworm

abundance (Drewry and Paton, 2000, Chan and Barchia, 2007) that are difficult, time

consuming and expensive to remedy (Bezuidenhout, 2010). In terms of empirical research, a

greater body of research has explored the causes and consequences of soil compaction on

arable soils rather than grasslands and much of the research conducted to-date originates

from New Zealand, Australia and the US (Drewry and Paton, 2000, Singleton and Addison,

1999, Clark et al., 2007, Greenwood et al., 1997, Naeth et al., 1990, Chan and Barchia, 2007)

with limited research conducted in a UK context (DEFRA, 2008). Within this body of literature,

key causes of soil compaction in agricultural production are related to farm machinery and

cattle grazing, where the weight of soil machinery and cattle compress the soil ((DEFRA, 2008,

Newell-Price et al., 2013).

Cattle grazing is central to dairy production and dairy farming is identified to be one of the

most significant contributors to soil compaction ((DEFRA, 2008, Newell-Price et al., 2013). The

cumulative impact of cattle treading on soil compaction rates has been well documented and

is recognised to cause the most visual and structural damage to soil surfaces (0-10 cm depths

(DEFRA, 2008) (see inter alia ((Drewry and Paton, 2000, Singleton and Addison, 1999, DEFRA,

2008, Wentworth, 2015). Sustained grazing and trampling of the soil by cattle results in


surface damage with less damage occurring at deeper soil levels. In the UK, the average time

that cattle spend grazing has increased over recent years from 7 months in 2006 to

approximately 9 months in 2010. Change has been underpinned by increasing feed prices and

the availability of early/late season grass and clover species and the increasing trend for out-

wintering cattle (Newell-Price et al., 2013). Soils vulnerability to structural damage caused as

a result of cattle trampling is subject to seasonal variations and is most susceptible during the

spring and autumn periods although, predisposed soils can also become more exposed at

times of high average rainfall when structural damage to the soil termed “pugging” or

“poaching” can result (DEFRA, 2008).

When animal hooves penetrate the surface of soils “poaching” occurs, this can arise across

fields although is often most pronounced around high-traffic areas within fields (i.e. around

feeding and water trays). Both cattle and sheep grazing can cause poaching that results in soil

compaction, although this occurs at greater intensity as a result of cattle grazing owing to the

increased pressures (kilopascal (kPa)) of cattle hooves, the volume of which differs between

static positions and when livestock is moving (Bilotta et al., 2007). To illustrate the impact of

cattle grazing it is useful to compare this to the impacts of sheep grazing. Sheep exert

approximately 80kPa which increases to 200kPa when moving. However, when static the

pressure exerted by cattle ranges from 160-192kPa, when in motion this more than doubles

(DEFRA, 2008).

Pugging occurs in wet conditions when soil pores fill with water significantly reducing the

macroporosity of soil. When cattle graze on saturated soil the soil structure can homogenise,

visually this results in lumpy and irregular surface and in extreme cases can result in slurry

(Parkes and Faulkner, 2013). Reduced macroporosity as a result of pugging has been show to

negatively affect plant production and the profitability as well as the sustainability of pastoral

farms (Burgess et al., 2000). Monitoring of soil compaction on dairy farms in New Zealand has

shown that a macroporosity value of <10% is likely to limit pasture production and in severe

cases could reduce this reduce production by 40-80%. Sever pugging events occurs most

during winter when block grazing occurs and cows are not being milked and soil recovery is

less effective than in spring and summer months (Parkes and Faulkner, 2013, Drewry et al.,

2004). Stocking density (i.e. the number of cows grazing) per hectare, is shown to be further

compounding factor in compaction rates, with increased cattle numbers shown to have a


positive relationship with soil compaction (Greenwood et al., 1997, DEFRA, 2008, Naeth et al.,

1990).

Despite a plethora of studies that have illustrated the detrimental effect on soil of cattle

treading, there is limited research that has been conducted to explore ways in which the

impact of this might be ameliorated (Burgess et al., 2000). Modifications to agronomic

practice are such as amendments to grazing management frequency and timing are thought

to minimise compaction ((Greenwood et al., 1997, Parkes and Faulkner, 2013, Drewry et al.,

2004). Restorative measures of which mechanical soil loosening is an example, have been

studied less widely. Mechanical loosening of the soil in order to break up compacted soils is a

strategy for the amelioration of soils that have been degraded as a result of cattle treading.

In a study conducted on two New Zealand dairy farms, Burgess et al. (2000)found that when

compared to non-aerated soils, mechanical loosening was advantageous in that it increased

macroporosity and total porosity and hydraulic conductivity as well as reducing water

penetration resistance the degree of packing and bulk density and improved conditions for

plant root growth. Reversion of the benefits of aeration occurred in the sample site after 40

weeks and therefore the research illustrated the need for this action to be repeated annually.

Such interventions that are designed to reduce compaction and increase soil quality deliver

direct economic benefits to farmers as well more widely to the rural communities in which

they are embedded, as well as society as a whole through improved food quality and

availability. Such practices also deliver wider conservation benefits through the delivery of

additional ecosystem services, including improved responsiveness to flooding events,

increased biodiversity and carbon and nitrogen regulation.

1.2 Need for the review This rapid evidence review aims to explore the impacts of mechanical soil loosening to

ameliorate soil compaction as an intervention to improve 1) productivity and 2) sustainability

in UK dairy farming. A number of studies have indicated the effectiveness of mechanical soil

loosening as a restorative intervention against soil compaction, caused by large ruminant

grazing including dairy production (Drewry and Paton, 2000, Burgess et al., 2000). Soil is a

fundamental eco-system services, protecting it and restoring it where degradation has

occurred has potential to ensure the productivity and sustainability of UK dairy farming.

However, there has been no formalised evaluation of the extant body of literature and the


strength of evidence of the effectiveness of mechanical soil loosening for improved dairy farm

productivity and sustainability has not been assessed.

This rapid evidence review will therefore, make a number of substantive contributions; to the

best of the authors knowledge this is the first time that published evidence of the

effectiveness of this intervention for improving soil quality has been synthesised. From a

policy perspective this will formalise the evidence base upon which decisions regarding the

promotion of mechanical soil loosening as an ‘Payment for Ecosystem Services’ intervention,

can be made. From an academic perspective evidence synthesis supports the identification of

knowledge gaps and helps to direct future research agendas.

2 Objectives

2.1 Primary objective: To evaluate the effectiveness of mechanical soil loosening to ameliorate soil compaction

caused by cattle grazing in diary production systems and the impacts of this intervention for;

1) Improved productivity (yield) and sustainability (i.e. improved soil quality and

biodiversity) of dairy farming.

2.2 Secondary objective: A number of secondary outcomes will also be examined and will be used to explore the

reasons for heterogeneity in the primary outcomes of the study. These include the impacts of

the following on the effectiveness of mechanical soil loosening;

x Soil type

x Herd size/stock density

x Compaction depth

x Soil saturation

x Seasonality/weather conditions

x Grazing management system

x Intervention frequency

2.3 Tertiary outcome: 1) Measurements of the economic impact of soil loosening by mechanical means


3 Criteria for considering studies for the review Studies obtained from the search will be selected based on the eligibility criteria outlined in

Table 1, any studies not meeting the inclusion criteria will be excluded. These are outlined in

more detail in the subsequent sections and are based on the PICO (population, intervention,

comparator, outcome) format.

Table 1: Inclusion/exclusion criteria

Inclusion criteria Exclusion criteria

Empirical (quantitative) studies conducted

between 1986-2018 in English language.

A non-empirical study i.e. review article or

posters or abstracts that were not followed

up by full publication, a non-English

language study or published prior to 1986.

studies with a comparator (i.e. adoption

versus non-adoption or a before/after

temporal comparison)

Studies without a comparative component.

Report on the impacts of compaction caused

by cattle treading of farm machinery

Report on the impacts of compaction not

caused by animal treading or farm

machinery

Report on impacts of soil loosening for

productivity and/or sustainability in

temperate grassland systems

Report on the impacts of soil loosening in

non-temperate grass land systems

Studies that examine methods or refine

tools for soil compaction alleviation

Studies must include sample size and mean

values to facilitate effect size generation.

Studies that do not report sample size and

mean values to enable effect size

generation.


3.1 Searches: Web of Science will be searched as well as Google Scholar in order to identify any grey

literature. Searches will cover all studies published over the past 32 years. Firstly, reference

lists of retrieved studies and reviews will be checked for additional studies not returned from

the initial searches. Secondly, key authors/organisations in the field will be consulted to check

for any unpublished findings and additional sources of information (Green and Higgins, 2005).

3.2 Search strategy: Search terms will be refined after trial searches are conducted, tailored to each database, to

balance sensitivity and specificity. The search strategies will be reported in an appendix in the

final review. The following search terms will be used. All search terms will be included in the

topic, keyword, title and abstract sections of each individual database searched and used in

conjunction with the Boolean operator AND as highlighted. Keywords in relation to the

comparator were not used as they were too generic and risk returning irrelevant papers.

The following search terms will be trailed:

(livestock OR cattle OR ruminant) AND ((Soil compaction) OR pugging OR poaching OR

treading) AND ((Soil loosening) OR (mechanical soil loosening) OR subsoiling) AND

(productivity OR yield OR sustainability OR (soil quality) OR macroporosity OR (bulk density)

OR (hydraulic conductivity) OR (plant root growth))

3.3 Domain of Study: A number of studies have indicated the effectiveness of mechanical soil loosening as a

restorative intervention against soil compaction, caused by large ruminant grazing including

dairy production (Burgess et al., 2000, Drewry and Paton, 2000) Soil is a fundamental eco-

system services, protecting it and restoring it where degradation has occurred has potential

to ensure the productivity and sustainability of UK dairy farming. However, there has been no

formalised evaluation of the extant body of literature and the strength of evidence of the

effectiveness of mechanical soil loosening for improved dairy farm productivity and

sustainability has not been assessed.

This rapid evidence review will therefore, make a number of substantive contributions; to the

best of the authors knowledge this is the first time that published evidence of the


effectiveness of this intervention for improving soil quality has been synthesised. From a

policy perspective this will formalise the evidence base upon which decisions regarding the

promotion of mechanical soil loosening as an PES intervention, can be made. From an

academic perspective evidence synthesis supports the identification of knowledge gaps and

helps to direct future research agendas

3.4 Participants/population: Studies conducted in any geographical region that assess the impact of mechanical soil

loosening as a method for the amelioration of soil compaction caused by cattle treading and

impacts of this for productivity and sustainability within temporal grassland systems.

3.5 Intervention(s)/exposure(s); Any studies that have adopted mechanical soil loosening as an intervention to ameliorate soil

compaction caused by cattle treading and the impacts of this for productivity within temporal

grassland systems.

3.6 Comparator(s)/control: Studies will be included on the basis that they report on 1) adoption versus non-adoption

and/or 2) temporal comparisons (i.e. before and after).

4 Method of the Review

4.1 Data extraction: All search results will be exported into an EndNote library, with duplicates being removed

before results are sifted according to the inclusion and exclusion criteria outlined in Table 1.

An overview of the search process will be included in a PRISMA flow chart (Moher et al., 2009).

The returned search results will then be filtered in a two -stage process as follows:

Stage 1) Title and abstract screening: In addition to the full title the abstract of these

studies will also be read so as to minimise the risk of error (Green and Higgins, 2005).

HK will review all studies, with a subset of at least 10% independently assessed by two

reviewers (HK and AT). Any differences between the two researchers will be reported

and resolved through discussion.

Stage 2) Full text screening: the full text of all included studies will be read and

assessed for relevance by the primary researcher (HK)A subset of at least 10% cross


checked between two reviewers (HK and AT). Any differences in decisions related to

study eligibility will be recorded and discussed by the review authors.

4.2 Risk of bias (quality) assessment The validity and the impact of bias will be addressed by use of a critical appraisal document(s)

that examines a number of quality criteria which have the potential to impact on the results

of the study. Critical assessment will consider the construct validity, internal validity and

reliability of included studies, as described by Yin (2009).

The quality appraisal tool will be modified from the Newcastle-Ottowa scale (NOS) to provide

a checklist that meets the emerging requirements of the review and suitable quality

assessment of non-medical research literature. (Green and Higgins, 2005), Campbell

Collaboration (2001) guidelines and the Centre for Reviews and Disseminations (2009) advice,

to provide a document not based in a healthcare context. The critical appraisal tool will be

finalised prior to data extraction.

No studies will be excluded based on the quality assessment tool, but the findings will be

taken into account during the evidence synthesis as part of the Grading of Recommendations,

Assessment, Development and Evaluation (GRADE) framework, (Meader et al., 2014) which

will assess the overall of strength of evidence, and may inform sensitivity analysis. Any

differences in decisions related to study quality will be discussed by the review authors

4.3 Strategy for data synthesis A data extraction form will be used to extract data from all included studies (excel), and this

will be finalised as the nature of the data becomes apparent. The finalised data extraction

form will be trialled, to check that all relevant information is extracted. A template of the final

form will be attached to the final review,

All data will be extracted by the primary researcher (HK), a subset of at least 10% of the

included studies will be checked independently by a second reviewer (AT), again to check for

potential errors. Where information is missing efforts will be made to contact the authors to

obtain further details (Green and Higgins, 2005).

An overview of all included studies will be provided in an appendix. Descriptive statistics, such

as a summary of the study characteristics, will first be presented in the results. Synthesis of

the data will depend on the nature of the included studies.


If we have a sufficient number of high quality studies a random effects meta-analysis will be

carried out using (standardized) mean difference. In order to do this, we will collect data on

means, standard deviations, and the number of replicates. Sensitivity analyses will be

performed to explore the risk of bias and a funnel plot will be used to detect potential

publication bias. If we do not have a sufficient number of high quality studies, we will use the

diverse set of literature in order to identify and evaluate reported outcomes.


5 References: BEZUIDENHOUT, R. 2010. Dealing with soil compaction – part 1 [Online]. Farmers Weekly. Available:

https://www.farmersweekly.co.za/farm-basics/how-to-crop/dealing-with-soil-compaction-part-1/ [Accessed 29th June 2018].

BILOTTA, G., BRAZIER, R. & HAYGARTH, P. 2007. The impacts of grazing animals on the quality of soils, vegetation, and surface waters in intensively managed grasslands. Advances in agronomy, 94, 237-280.

BURGESS, C. P., CHAPMAN, R., SINGLETON, P. L. & THOM, E. R. 2000. Shallow mechanical loosening of a soil under dairy cattle grazing: Effects on soil and pasture. New Zealand Journal of Agricultural Research, 43, 279-290.

CHAN, K. & BARCHIA, I. 2007. Soil compaction controls the abundance, biomass and distribution of earthworms in a single dairy farm in south-eastern Australia. Soil and Tillage Research, 94, 75-82.

CLARK, D., CARADUS, J., MONAGHAN, R., SHARP, P. & THORROLD, B. 2007. Issues and options for future dairy farming in New Zealand. New Zealand journal of agricultural research, 50, 203-221.

DEFRA 2008. Scoping study to assess soil compaction affecting upland and lowland grassland in England and Wales Department for Environment and Rural Affairs.

DREWRY, J. 2006. Natural recovery of soil physical properties from treading damage of pastoral soils in New Zealand and Australia: a review. Agriculture, Ecosystems & Environment, 114, 159-169.

DREWRY, J. & PATON, R. 2000. Effects of cattle treading and natural amelioration on soil physical properties and pasture under dairy farming in Southland, New Zealand. New Zealand Journal of Agricultural Research, 43, 377-386.

DREWRY, J., PATON, R. & MONAGHAN, R. 2004. Soil compaction and recovery cycle on a Southland dairy farm: implications for soil monitoring. Soil Research, 42, 851-856.

FAO. 2015. Healthy soils are the basis for healthy food production [Online]. Food and Agriculture Organisation of the United Nations. Available: http://www.fao.org/soils-2015/news/news-detail/en/c/277682/ [Accessed 29th June 2018].

GREEN, S. & HIGGINS, J. 2005. Cochrane handbook for systematic reviews of interventions. Version. GREENWOOD, K., MACLEOD, D. & HUTCHINSON, K. 1997. Long-term stocking rate effects on soil

physical properties. Australian Journal of Experimental Agriculture, 37, 413-419. MEADER, N., KING, K., LLEWELLYN, A., NORMAN, G., BROWN, J., RODGERS, M., MOE-BYRNE, T.,

HIGGINS, J. P., SOWDEN, A. & STEWART, G. 2014. A checklist designed to aid consistency and reproducibility of GRADE assessments: development and pilot validation. Systematic reviews, 3, 82.

MOHER, D., LIBERATI, A., TETZLAFF, J. & ALTMAN, D. G. 2009. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. Annals of internal medicine, 151, 264-269.

NAETH, M., PLUTH, D., CHANASYK, D., BAILEY, A. & FEDKENHEUER, A. 1990. Soil compacting impacts of grazing in mixed prairie and fescue grassland ecosystems of Alberta. Canadian Journal of Soil Science, 70, 157-167.

NEWELL-PRICE, J., WHITTINGHAM, M., CHAMBERS, B. & PEEL, S. 2013. Visual soil evaluation in relation to measured soil physical properties in a survey of grassland soil compaction in England and Wales. Soil and Tillage Research, 127, 65-73.

NFU. 2016. Backing British Dairy: Our Q&A [Online]. NFU. Available: https://www.nfuonline.com/sectors/dairy/dairy-news/backing-british-dairy-our-qa/ [Accessed 03/09 2018].

PARKES, R. & FAULKNER, T. 2013. Soil compaction and pugging on dairy farms. In: GREATER WELLINGTON REGIONAL COUNCIL (ed.).

SINGLETON, P. & ADDISON, B. 1999. Effects of cattle treading on physical properties of three soils used for dairy farming in the Waikato, North Island, New Zealand. Soil Research, 37, 891-902.


SMITH, S., ROWCROFT, P., EVERARD, M., COULDRICK, L., REED, M., ROGERS, H., QUICK, T., EVES, C. & WHITE, C. 2013. Payments for Ecosystem Services: A Best Practice Guide. In: DEPARTMENT FOR ENVIRONMENT AND RURAL AFFAIRS (ed.). London: DEFRA.

WENTWORTH, J. 2015. Securing UK Soil Health. In: PARLIMENTARY OFFICE OF SCIENCE AND TECHNOLOGY (ed.). London.

YIN, R. K. Case study research: Design and methods 4th ed. United States: Library of Congress Cataloguing-in-Publication Data, 2009.


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A protocol for rapid evidence synthesis into soil loosening as an … · 2018-09-07 · A protocol...

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